Tubular writing tip having an outer reduced diameter portion

ABSTRACT

In a nib structure of a writing instrument of the type having a tubular nib fitted to a forward end of a tubular tip of the instrument, the tubular nib is provided with a concentrically reduced diameter portion having an outer surface gently sloped from the ends toward a middle portion of the nib, and a radiused peripheral edge at a rearward end of the nib. The nib structure provides easy and accurate fitting of the nib into the tubular tip.

This application is a continuation of now abandoned Ser. No. 361,929,filed Mar. 10, 1982.

TECHNICAL FIELD

This invention relates to a nib structure of a writing instrument havinga tubular writing tip wherein a tubular nib made of hard materialshaving hardwearing properties is mounted to an end of the tubularwriting tip.

BACKGROUND ART

A writing instrument having a tubular writing tip connected to an end ofa barrel or casing is known, in which ink is fed from an ink reservoirin the barrel to the tubular writing tip. In such a writing instrument,an axially slidable needle or rod is usually provided within the tubularwriting tip so as to improve ink feeding.

The writing instrument of the type as described has been used primarilyby draftsmen. For drafting, synthetic resin films treated to have arough surface, such as by sandblasting and chemical mats, have beenused, which, however, cause remarkable wearing of the tubular writingtip. In order to minimize such wear, an attempt has been made in whichan additional tubular nib made of a hard materials having highwear-resistant properties such as a metal, for example hard stainlesssteel, chrome-plated brass and the like, precious stones such as rubyand the like, or ceramics, is fitted to an end of the aforementionedtubular writing tip.

The tubular nib is conventionally fitted to the tubular writing tip byemploying desired adhesive agents or by press-fitting. During connectionby the adhesive agents, the tubular nib is formed with its outerdiameter being smaller than an inner diameter of the tubular writing tipso that an annular space is formed between the nib and the tip, and theadhesive agent is supplied into the space. During the press-fittingconnection, the tubular nib is formed with its outer diameter beingsubstantially equal to, or slightly larger than, the inner diameter ofthe tubular tip, and the nib is forcibly inserted into the tip.

In the connection by the adhesive agent, however, it is quite difficultto hold both the annular nib and the annular tip in accurate positionswith their axes being aligned with each other since the annular space orgap between the nib and the tip must be formed for inserting therein theadhesive agent. When both the annular nib and the tip are not accuratelypositioned, thus resulting in non-alignment of their axes, a constantflow of ink will not be expected, and a smooth axial movement of aneedle or rod will not be established when the writing instrument is ofthe type which employs such needle or rod in the tubular tip. In thepress-fitting connection, finishing of highest precision is required forthe nib and tip since the outer diameter of the nib and the innerdiameter of the tip must be controlled with strict dimensional accuracy.To be more specific, an outer diameter of the nib larger than thepredetermined dimension will not permit the nib to be inserted into thetip and, on the other hard, a smaller diameter of the nib willapparently fail to firmly connect the two elements together. Besides,even though both the nib and the tip could be formed in a desireddimensional accuracy, problems are still unsolved in that the moreaccurately are the elements formed, the more accurate must be thepress-fitting operation. If a deviation, however small it may be, isproduced between the nib-advancing direction and the axial direction ofthe nib, an excessive thrust is needed to press the nib further into thetip. Such excessive thrust will cause the two elements to be deformed ordamaged.

The aforesaid problems encountered during the connection of the elementsare due to the fact that both the nib and the tip are extremely smallsized, and that even the smallest deviations in the press-fittingdirection and in dimensional accuracy result in a larger disadvantageouseffect.

SUMMARY OF THE INVENTION

An object of this invention is to provide a nib structure of a writinginstrument of the type having a tubular writing tip, which can overcomethe aforesaid problems encountered in the conventional operation forpress-fitting a tubular nib to the tip, and establish a fine adjustmentof deviation of the inserting directions of the nib when such deviationsare formed during a press-fitting operation of the nib.

According to this invention, there is provided a nib structure of awriting instrument of the type having a tubular nib fitted to a forwardend of a tubular tip of the instrument, characterized in that thetubular nib is provided with a concentrically reduced diameter portionhaving an outer surface gently sloped toward a middle portion of thenib, and a radiused peripheral edge at a rearward end of the nib.

The inventive nib structure has an advantage that a fine adjustment ofthe pressing direction of the tubular nib can easily and effectively beestablished by coaction of a space produced between the outer surface ofthe reduced diameter portion of the nib and the inner surface of thetubular tip and the radiused edge at the rearward end of the nib, evenwhen the nib has been inaccurately inserted such that the pressingdirection of the nib is not aligned with the axial direction of the nib.

In the present invention, the tubular nib can be connected by thepress-fitting method. However, if necessary, a desired adhesive agentmay be employed in addition to press-fitting.

Preferred embodiments of this invention will be hereinbelow described indetail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a sectional view of an embodiment according to the invention;

FIG. 2 is an enlarged perspective view of a tubular nib;

FIG. 3 is a perspective view of the tubular nib, showing the nib in apress-fitting operation; and

FIGS. 4, 5, 6 and 7 are sectional views of other embodiments accordingto the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1 which shows an embodiment of the invention, atubular nib 2 is press-fitted to an end of a tubular tip 1. The tubularnib 2 is forcibly inserted into the tubular tip 1 until the rearward endof the nib 2 abuts against a shoulder 3 disposed on the inner surface ofthe tip 1, with the forward end of the nib 2 projecting slightly beyondthe end of the tip 1 to form a writing point. Reference numberal 10represents a forward end portion of a barrel of the writing instrument,and may be formed integral with the tubular tip 1.

As will be understood from FIG. 2, the tubular nib 2 is provided with aconcentrically reduced diameter portion 4 having an outer surface gentlysloped from the ends toward a middle portion of the nib 2 and a radiusedportion 5 at the peripheral edge of a rearward end of the nib 2.

The tubular nib 2 having the reduced diameter portion 4 and radiusededge 5 may be manufactured by, for example, injection-molding acylindrical nib and then grinding or barrelling it to make the finishednib. It may be possible, of course, to manufacture a tubular nib 2having the reduced diameter portion 4 and the radiused edge 5 directlyby using injection molding. In the present invention, any suitablemethods may be selected or combined according to the desired shapes ordimensions of the reduced diameter portion and the radiused edge of thenib 2.

The tubular nib 2 is typically designed to have a length of 3 mm, anouter diameter of 0.6 mm and an inner diameter of 0.3 mm, with areduction of the outer diameter at the reduced diameter portion being0.05 mm and a radiused edge being 0.2 mm R. It should be understood,however, that these dimensions are merely an example and this inventionis not limited to these dimensions, but an excessive reduction of theouter diameter at the reduced diameter portion results in a decrease instrength of the tubular nib 2 itself.

FIG. 3 illustrates maladjustment wherein the axial direction of the nib2 is not correctly aligned with the nib-inserting direction, themaladjustment being often seen during the process of press-fitting ofthe nib 2 into the tubular tip 1. As described above, it is likely thatsuch maladjustment or non-alignment often occurs in the process ofpress-fitting by using chuck means or by hand (not shown), and suchnon-alignment becomes a serious obstacle to a further press-fitting.According to the present invention, the press-fitting operation can becontinued by correcting the non-alignment which can be accomplished dueto the existence of the reduced diameter portion 4 and the radiused edge5 of the nib 2. In other words, when the tubular nib 2 has been insertedinto the tubular tip 1 in the state of non-alignment as illustrated inFIG. 3, the radiused edge 5 is in line contact with an inner surface ofthe tubular tip 1, and the gentle slope of the reduced outer diameterportion of the nib 2 functions to guide the movement of the nib forcorrection of the non-alignment along a forward inner edge of thetubular tip 1, so that the tubular nib 2 can be further inserted withthe non-alignment being corrected.

Other embodiments according to the present invention will be describedwith reference to FIGS. 4 through 7 in which FIGS. 4 and 5 show specificstructure for securing the tubular nib 2 relative to, and in alignmentwith, the tubular tip 1 and for preventing the tubular nib 2 fromleaving the tubular tip 1 after the press-fitting of the two elements.In FIG. 4, a protrusion 6 is formed at the inner surface of the tubulartip 1 by pressing a part or the entire annular part of the outer surfaceof the tubular tip 1, so that the protrusion 6 abuts against apredetermined portion of the reduced diameter portion 4 of the nib. FIG.5 shows an adhesive agent 7, which is applied on an outer surface of thereduced diameter portion 4 during or after the step of press-fitting ofthe tubular nib 2 into the tubular tip 1. Hardening of the adhesiveagent prevents more effectively slipping-out of the nib 2. In theembodiment of FIG. 5 employing the adhesive agent, ink leakage, whichwill often occur through a minor gap between the tip 1 and nib 2, can beprevented. Besides, when a crack or split is produced in the tubular nib2 as a result of the press-fit operation such crack or split can bereinforced by the adhesinve agent. The use of an anaerobic adhesiveagent containing tetraethylene glycol dimethacrylate as a mainingredient is preferred, because the anaerobic adhesive agent 7 appliedto the area between the nib 2 and the tip 1 will gradually be hardenedfrom the rear portion of the nib, i.e. the air-isolated portion. Ifdesired, the adhesive agent can be applied to the structure of FIG. 4.

FIG. 6 shows a further modified structure embodying the invention, inwhich an annular member 8 is inserted into the tubular tip 1 forlimiting the insertion of the tubular nib 2. The annular member 8functions as the shoulder 3 of the structure of FIG. 1 and makes itpossible to eliminate difficulties of forming the shoulder 3.

FIG. 7 shows another embodiment of the invention in which tubular nib 2is designed to have an inner diameter smaller than the inner diameter ofthe tubular tip 1 so that a greater capillary action is produced withintubular nib 2 than within the tubular tip 1.

As described above, the tubular nib, which is fitted in a tubular tip ofthe writing instrument, has a gently sloped outer surface to form areduced diameter portion and a radiused peripheral edge at its rearwardend. Accordingly, a deviation of accuracy, which likely occurs duringthe step of insertion of the nib into the tubular tip, can be corrected,and press-fitting as well as application of an adhesive agent can beeffected. Further, axial non-alignment between the nib and the tip canbe readily corrected, and constant and continuous flow of ink can beobtained.

The above-illustrated embodiments can be modified within the scope ofthe basic structure of the invention. For example, all of theillustrated embodiments show the tubular nib 2 of a symmetrical designin which the both rear and fore ends of the nib have radiused edges.Such symmetrical design eliminates the difficulty of finding which endshould be inserted into the tubular tip 1. However, the ends of the nib2 may be formed assymmetrically if the writing properties are notreduced. In order to eliminate a gap or space between an outer surfaceof the tubular nib 2 and a forward inner end of the tip 1, the tip maybe provided with a reduced inner diameter portion at its fore end.Further, the annular member 8 illustrated in FIG. 6 may be deleted sothat the tubular nib 2 is inserted into the tip 1 until the rear end ofthe nib 2 abuts against the wall of the barrel 10.

We claim:
 1. In a writing instrument nib structure of the type includinga tubular nib press-fitted into a forward end of a tubular tip of theinstrument, the improvement of means for enabling press-fitting of saidnib into said tip upon misalignment of the longitudinal axis of said niband the direction of pressing by correcting such misalignment duringpressing, said means comprising:an outer nib surface defining equallyconfigured radiused peripheral edges at opposite longitudinal ends ofsaid nib, said outer nib surface sloping radially inwardly from saidradiused peripheral edges toward a middle length portion of said nib,thereby defining a concentrically reduced diameter central portion, suchthat said nib is longitudinally symmetrical between said opposite ends;and said radiused peripheral edge at a rearward end of said nibcontacting an inner surface of said tip, and said sloping surface ofsaid nib and said inner surface of said tip defining therebetween anannular space; whereby said sloping surface acts to guide pressingmovement of said nib while correcting misalignment thereof.
 2. Theimprovement claimed in claim 1, further comprising an adhesive agentprovided in said space between said sloping surface of said nib and saidinner surface of said tip.
 3. The improvement claimed in claim 1,further comprising a protrusion extending from said inner surface ofsaid tip inwardly into said space and abutting said reduced diameterportion of said nib.
 4. The improvement claimed in claim 3, furthercomprising an adhesive agent provided in said space between said slopingsurface of said nib and said inner surface of said tip.